The invention concerns a process for manufacturing a sensor arrangement for temperature measurement comprising a temperature-sensitive measuring resistance which has a thin metal film as a resistance layer and contact surfaces on a ceramic substrate, wherein the resistance layer is covered by an electrically insulating protective layer. The contact surfaces are, however, electrically conductive and are directly and firmly connected with conductor paths, which are electrically insulated from one another, on a high temperature-resistant carrier element, wherein the measuring resistance is bonded on one end of the carrier element, and on the end of the carrier element facing away from the measuring resistance, contact surfaces are arranged for connecting a contact clip, plug or cable.
A process for bonding electrical conductors in the form of fine wires or bands with electrical conductor paths is known from German published patent application DE 34 24 387 A1. According to this publication, Pt wires with a diameter of about 0.1 to 0.5 mm are connected electrically and mechanically fixed on a ceramic substrate, in which a thick layer paste is applied to the conductor paths on the ceramic substrate. The wires are laid into this paste and run through a firing process together with the paste.
Furthermore, printed circuit boards are adequately known as carrier elements for passive or active components, for example from German patent DE 39 39 165 C1 or German utility model DG 87 16 103 U1. Since most of these components find applications in the temperature range up to a maximum of 150.degree. C., the board material is also usually designed only for this temperature range. As a rule, these materials are plastics, which are often reinforced with inorganic materials. To the extent that a wireless bonding of the components is provided, as is typical, for example, also with temperature measurement resistances for application as calorimetric sensors (see German patent DE 44 24 630 C1), this takes place with soft solder and/or by means of conductive glue. These connection techniques to plastic boards are, however, completely unsuited for temperatures above 300.degree. C.
A sensor arrangement, likewise for calorimetry, is known from German utility model DE 295 04 105 U1, in which a short (15 mm long) ceramic layer is used as a carrier element. Since use as a calorimetric sensor is indicated here as well, one must assume that the bonding is provided by soft solder, which likewise only permits a maximum operating temperature of 300.degree. C.
Further procedures for producing sensor arrangements with temperature measuring resistances for high temperature applications according to the state of the art (described, for example, in German utility models DGm 1,784,455 and DGm 1,855,262) are so designed that first the connection wires of the measuring resistance are lengthened by electrically insulated connection wires of the connection circuit. The connection from the rather thin connection wire of the measuring resistance to the considerably thicker connection wire of the supply circuit is produced by welding or hard soldering. If a fiber glass-jacketed supply lead is used, it must first be stripped. In order to rule out a short circuit during operating conditions, an electrical insulation for the connection wires of the measuring resistance and for the area of the weld or hard solder joint must be provided in some form. Moreover, the connection wires must be relieved from traction either by cast masses or special ceramic molded parts (see DGm 1,855,262).
The electrical insulation of the connection circuit for high temperature use is accomplished either with ceramic capillary tubes, which, however, constitute a large proportion of the overall material costs and often stand in the way of miniaturization due to their geometrical dimensions, or is ensured by fiberglass casings, which are stiffened by an organic impregnation for production reasons. This impregnation must be removed in an extra firing process. For fixing the position of the measuring resistance, it is furthermore customary to introduce a ceramic adhesive into the tip of the measuring unit protective tube. According to the prior art, a high temperature measuring unit is thus produced with a great number of individual parts and process steps, which either cannot be automated at all, or are automatable only at great expense.